Thermoplastic composite pipe with multilayer intermediate lamina

ABSTRACT

A process for producing a thermoplastic composite pipe is provided. The thermoplastic composite pipe thus produced contains a liner, two or more composite layers composed of tape laminas, and a single- or multilayer intermediate lamina arranged between different composite layers. Composite formation between identical polymers in the process achieves improved adhesion. The thermoplastic composite pipe is especially suitable for offshore applications in oil or gas production.

The invention provides a flexible fibre-reinforced composite pipecomprising an inner liner (also called “liner” for short hereinafter),two or more composite layers composed of tape laminas, and a single- ormultilayer intermediate lamina which is arranged between differentcomposite layers and bonds them, and a process for production thereof.The material for the inner liner, the matrix for the tape laminas andthe polymers for the intermediate lamina are thermoplastic. Thecomposite pipe according to the invention is used for oil and gasproduction, especially for the offshore production of oil or gas, as ariser, as an umbilical, for the transport of the produced oil or gasacross the seabed from the well to the riser, or for transport on land.

In the prior art, what are called unbonded flexible pipes are veryfrequently used for this application sector. Pipes of this kind comprisean inner lining, typically in the form of a plastic pipe, as a barrierto the exit of the fluid being conveyed, and also one or more armourlayers on the outside of this inner lining. The unbonded flexible pipemay comprise additional layers, for example one or more armour layers onthe inside of the inner lining, in order to prevent the collapse of theinner lining under high external pressure. Such an inner armour istypically referred to as carcass. In addition, an outer shell may bepresent in order to provide a barrier against the ingress of liquid fromthe outside environment into the armour layers or polymeric or metallicfunctional layers further to the inside, and as protection againstoutside mechanical stresses.

Typical unbonded flexible pipes are described by way of example in WO01/61232, U.S. Pat. Nos. 6,123,114 and 6,085,799; they are moreoverdescribed in more detail in API Recommended Practice 17B, “RecommendedPractice for Flexible Pipe”, 3rd edition, March 2002, and also in APISpecification 17J, “Specification for Unbonded Flexible Pipe”, 2ndEdition, November 1999.

The term “unbonded” in this context means that at least two of thelayers, inclusive of reinforcing layers and plastics layers, do not haveany mutual adhesive bonding. In practice, the pipe comprises at leastthree armour layers which, over the entire length of the pipe, have nomutual bonding either directly or indirectly, i.e. by way of otherlayers. This renders the pipe flexible to an extent that allows it to berolled up for transport purposes.

In conventional unbonded flexible pipes, the armour layer(s) usuallyconsist(s) of steel wires, steel profiles or steel strips arranged inthe form of a spiral, where the individual layers may be formed withdifferent winding angles relative to the pipe axis (tensile armour), andpressure armour wound primarily in the circumferential direction. Insuch unbonded flexible pipes, the steel component is exposed to thecorrosive effects of the medium being conveyed. Owing to the resultingchoice of material and the complex construction, pipes of this kind arecomparatively costly. The high intrinsic weight is very disadvantageousespecially in the case of relatively long risers for offshore oilproduction in deep seas.

For some time, there have been descriptions of developments wherethermoplastic composite pipes are employed. These are pipes having, asinner lamina, a single- or multilayer inner liner composed ofthermoplastic material. A composite lamina is applied thereto, in acohesively bonded or in some cases even unbonded manner, for example bywinding of unidirectionally fibre-reinforced tapes. Composite pipes ofthis kind are disclosed, for example, in WO 95/07428 and WO 99/67561.The production thereof is additionally described in WO 02/095281, WO2006/107196, WO 2012/118378, WO 2012/118379 and WO 2013/188644.

It is a general problem in the case of these composite pipes that thebonding between a fibre-rich tape lamina and the adjoining surface inthe case of a suboptimal material combination is inadequate to withstandthe stresses in installation and operation, especially in offshoreapplications, such as attachments to fittings or mounting with grippingdevices, and the hard test conditions to which constructions of thiskind are subjected. Mention is made here by way of example of thedetachment of layers in the rapid gas decompression test or under theaction of significant bending forces. Attempts are therefore being madein the prior art preferably to use polymer of the same kind for the tapematrix and an adjoining surface, for example the outer surface of theinner liner (see, for instance, “Thermoplastic Composite Pipe: AnAnalysis And Testing Of A Novel Pipe System For Oil & Gas”; presentationby J. L. C. G. de Kanter and J. Leijten at the ICCM 17 conference inEdinburgh, U K, 2009).

In the case of thermoplastic composite pipes with single-wall liners,liner pipes made of polyethylene are used in the low-temperature range(sustained temperature up to about 50° C.), and liner pipes made ofpolyamide such as PA11 or PA12 at higher temperatures up to about 80° C.At even higher temperatures, high-cost materials such as polyvinylidenedifluoride (PVDF) or even polyether ether ketone (PEEK) are used. Takingaccount of the demands on chemical stability, ageing resistance andthermal stability, it is possible in many cases to use compositecomprising a matrix composed of PA11 or PA12. It is frequently found tobe appropriate to form the composite lamina from different compositelayers, where the different composite layers each have a matrix based ondifferent polymers. Thus, in many cases, the matrix of the compositelayer arranged on the outside may be based on a polymer which is cheaperor has elevated flexibility. This is possible since the outer region ofthe pipe wall is subject to lower demands with regard to thermalstability, stability toward the medium to be conveyed, and diffusionbarrier action. However, a question that generally arises in the case ofcombination of unlike materials is how the necessary adhesion is to beachieved between different composite layers.

The person skilled in the art is aware that the composite can be formedfrom two different thermoplastic layers with one another either viamaterial compatibility or via chemical reactions. Material compatibilityexists in the ideal case when the same polymer is involved. It is knownfrom experience with multilayer pipe development and multicomponentinjection moulding that chemical bonds can be achieved quite efficientlywith elevated temperature and residence time when melt is applied tomelt, for example in coextrusion. However, good adhesion of theidentical material combination is much more difficult to achieve when asolidified surface first has to be surface-melted by a hot melt and onlylittle time is available for a chemical reaction. Even in the case ofpolymers of the same kind, a bond thus established can have inadequatestrength. A better composite arises when the two composite partners aremelted at the surface thereof prior to joining and then pressed againstone another. However, here too, the time for a chemical reaction isshort, and so the bonds between equivalent polymers generally havebetter adhesion than bonds that have to be implemented through achemical reaction or via material compatibility (i.e. through diffusionprocesses).

The problem addressed by the invention is that of providing a processfor producing a thermoplastic composite pipe with which, firstly, highdegrees of freedom are achieved in the material combination of liner,tape matrix of the first composite layer and tape matrix of thesubsequent composite layer, and which secondly gives very good adhesionat the critical layer boundaries.

The underlying problem is solved in that tape laminas based on differentpolymers are bonded to one another so as to produce a film, one surfaceof which comprises the polymer B of the first composite layer and theother surface of which comprises the polymer C of the subsequentcomposite layer. The film is then bonded to the first composite layerwith application of heat and, in a further step, bonded to the firsttape lamina of the subsequent composite layer with application of heat.

FIG. 1 provides a representation of one embodiment of the thermoplasticcomposite pipe of the present invention.

The invention thus provides a process for producing a thermoplasticcomposite pipe, comprising the following steps:

-   a) providing a tubular liner having a wall comprising a    thermoplastic polymer A in the region of the outer surface;-   b) providing a tape comprising reinforcing fibres in a matrix    comprising a thermoplastic polymer B;-   c) providing a tape comprising reinforcing fibres in a matrix    comprising a thermoplastic polymer C;    where polymer A and polymer B are the same or different and polymer    B and polymer C are different,-   d) applying a tape provided in step b) to the tubular liner by means    of welding,-   e) optionally cohesively bonding further tape laminas of the same    kind to the tape lamina applied in step d),-   f) applying a film or a composite which is produced in step g) and    is composed of a film and a tape provided in step c) to the first    composite layer thus formed, with melting of the outer surface of    the first composite layer and of the contact surface of the film    either beforehand, simultaneously or thereafter, where the region of    the contact surface of the film consists of a moulding compound    comprising polymer B to an extent of at least 30% by weight,    preferably to an extent of at least 40% by weight, more preferably    to an extent of at least 50% by weight, especially preferably to an    extent of at least 60% by weight and most preferably to an extent of    at least 70% by weight, and where the region of the opposite (outer)    surface of the film consists of a moulding compound comprising    polymer C to an extent of at least 30% by weight, preferably to an    extent of at least 40% by weight, more preferably to an extent of at    least 50% by weight, especially preferably to an extent of at least    60% by weight and most preferably to an extent of at least 70% by    weight;-   g) applying the tape provided in step c) to the outer surface of the    film, with melting of the outer surface of the film applied and of    the contact surface of the tape either beforehand, simultaneously or    thereafter;-   h) optionally cohesively bonding further tape laminas of the same    kind to the tape lamina applied in step g),    where the second composite layer is produced in steps g) and    optionally h),-   i) optionally finally applying an outer cover lamina composed of a    polymeric material.

In a first embodiment, polymer A and polymer B are the same. In thiscase, in step d), the tape is applied directly to the outer surface ofthe liner, with melting of the outer surface of the liner and of thecontact surface of the tape either beforehand, simultaneously orthereafter.

In a second embodiment, polymer A and polymer B are different. In thiscase, tape and liner are bonded to one another so as to produce a film,one surface of which comprises the polymer A of the liner surface andthe other surface of which comprises the polymer B of the tape matrix.The film is then bonded to the liner with application of heat and, in afurther step, bonded to the first tape lamina with application of heat.Thus, the same concept as in the bonding of different composite layersis used. Step d) here thus consists of the following components steps:

-   d1) applying a film or a composite which is produced in step d2) and    is composed of a film and a tape provided in step b) to the tubular    liner, with melting of the outer surface of the liner and of the    contact surface of the film either beforehand, simultaneously or    thereafter, where the region of the contact surface of the film    consists of a moulding compound comprising polymer A to an extent of    at least 30% by weight, preferably to an extent of at least 40% by    weight, more preferably to an extent of at least 50% by weight,    especially preferably to an extent of at least 60% by weight and    most preferably to an extent of at least 70% by weight, and where    the region of the opposite (outer) surface of the film consists of a    moulding compound comprising polymer B to an extent of at least 30%    by weight, preferably to an extent of at least 40% by weight, more    preferably to an extent of at least 50% by weight, especially    preferably to an extent of at least 60% by weight and most    preferably to an extent of at least 70% by weight;-   d2) applying the tape provided in step b) to the outer surface of    the film, with melting of the outer surface of the film applied and    of the contact surface of the tape either beforehand, simultaneously    or thereafter.

The invention is to be elucidated in detail hereinafter, where theseelucidations, unless stated otherwise, explicitly relate equally to thefirst and second embodiments.

The tubular liner generally has an internal diameter in the range from15 to 400 mm, preferably in the range from 20 to 300 mm and morepreferably in the range from 25 to 255 mm. Its wall thickness isgenerally in the range from 2 to 40 mm, preferably in the range from 2.5to 30 mm and more preferably in the range from 3 to 20 mm. The liner mayhave a single layer or multiple layers. If it has a single layer, itconsists of a moulding compound comprising at least 30% by weight,preferably at least 40% by weight, more preferably at least 50% byweight, even more preferably at least 60% by weight and especiallypreferably at least 70% by weight, at least 80% by weight or at least85% by weight of the polymer A, based in each case on the overallmoulding compound. If the liner has multiple layers, the outer layerconsists of this moulding compound; the inner layer may consist of amoulding compound having, for example, a barrier effect or a chemicalprotection function with respect to components of the medium to beconveyed. Inner and outer layers may be bonded to one another by anadhesion promoter layer.

The polymer A may, for example, be a polyolefin, a polyamide, apolyphthalamide (PPA), a polyethylene naphthalate, a polybutylenenaphthalate, a fluoropolymer, a polyphenylene sulphide (PPS), apolyether sulphone, a polyphenyl sulphone (PPSU) or a polyarylene etherketone such as PEEK or PEK. In a preferred embodiment, the mouldingcompound of the single-layer liner or the moulding compound of the outerlayer of a multilayer liner does not comprise any further polymer asidefrom the polymer A.

The tapes provided in steps b) and c) comprise reinforcing fibres. Thesemay, for example, be glass fibres, carbon fibres, aramid fibres, boronfibres, ceramic fibres (for example composed of Al₂O₃ or SiO₂), basaltfibres, silicon carbide fibres, polyamide fibres, polyester fibres,fibres of liquid-crystalline polyester, polyacrylonitrile fibres, andfibres of polyimide, polyether imide, polyphenylene sulphide, polyetherketone or polyether ether ketone. Preference is given here to glassfibres, carbon fibres, aramid fibres and basalt fibres. The crosssection of the fibres may for example be circular, rectangular, oval,elliptical, or cocoon-shaped. With fibres of cross section deviatingfrom the circular shape (for example flat glass fibres) it is possibleto achieve a higher fill level of fibre in the finished part, and thushigher strength. The fibres may be used in the form of short fibres orlong fibres, or preferably in the form of endless fibres, for instancein the form of a weave or more preferably in the form of aunidirectional fibre lamina.

The proportion by volume of the reinforcing fibres in the tape isgenerally 10% to 85%, preferably 15% to 80%, more preferably 20% to 75%and especially preferably 25% to 70%.

In the tapes provided in steps b) and c), the type of reinforcing fibresand the proportion by volume thereof may be different.

The matrix of each of these tapes consists of a moulding compoundcomprising at least 30% by weight, preferably at least 40% by weight,more preferably at least 50% by weight, even more preferably at least60% by weight and especially preferably at least 70% by weight, at least80% by weight or at least 85% by weight of the polymer B or of thepolymer C, based in each case on the overall moulding compound. Thepolymer B or the polymer C may, for example, be a polyolefin, apolyamide, a polyphthalamide (PPA), a polyethylene naphthalate, apolybutylene naphthalate, a fluoropolymer, a polyphenylene sulphide(PPS), a polyether sulphone, a polyphenyl sulphone (PPSU) or apolyarylene ether ketone such as PEEK or PEK. Polymer B and polymer Care different. This means that they are different in terms of chemicalcomposition; differences in molecular weight, in the degree of branchingor in the end groups are immaterial. The same applies in the secondembodiment to the differing nature of polymer A and polymer B.

The tapes can be produced by any prior art method. The production ofunidirectional endless fibre-reinforced tapes is described in detail,for example, in EP 0 056 703 A1, EP 0 364 829 A2, U.S. Pat. No.4,883,625, WO 2012/149129, WO 2013/188644 and WO 2014/140025. Possibleproduction methods are, for example, melt application, impregnation witha polymer solution and removal of the solvent, film impregnation orpowder impregnation.

Typically, the tape used has a width of 5 to 500 mm and preferably awidth of 8 to 200 mm, while the thickness is typically in the range from0.1 to 1 mm, preferably in the range from 0.1 to 0.5 mm and morepreferably in the range from 0.15 to 0.35 mm. The overall compositelamina, i.e. the sum total of all the tape laminas or composite layers,here is in the range from 1 to 100 mm, preferably in the range from 5 to90 mm and more preferably in the range from 10 to 80 mm. For differenttape laminas, it is possible to use different tape geometries. The tapesused may have any suitable cross section. Furthermore, it is possible touse different reinforcing fibres for different tape laminas.

The polymers mentioned by way of example for polymer A, polymer B andpolymer C are well known to those skilled in the art and arecommercially available in a multitude of commercial grades, andtherefore there is no need for any more specific description. Examplesof useful polyolefins include polypropylene, polyethylene andcrosslinked polyethylene. Suitable polyamides are, for example, PA6,PA66, PA610, PA88, PA8, PA612, PA810, PA108, PA9, PA613, PA614, PA812,PA128, PA1010, PA10, PA814, PA148, PA1012, PA11, PA1014, PA1212 andPA12, or a polyether amide or polyether ester amide based on one ofthese polyamides. The polyphthalamide may, for example, be PA66/6T,PA6/6T, PA6T/MPMDT (MPMD stands for 2-methylpentamethylenediamine),PA9T, PA10T, PA11T, PA12T, PA14T, PA6T/61, PA6T/10T, PA6T/12, PA10T/11,PA10T/12 or PA612/6T. Suitable fluoropolymers are, for example,polyvinylidene fluoride (PVDF), ethylene-tetrafluoroethylene copolymer(ETFE), an ETFE modified with the aid of a tertiary component, forexample propene, hexafluoropropene, vinyl fluoride or vinylidenefluoride (for example EFEP), ethylene-chlorotrifluoroethylene copolymer(E-CTFE), polychlorotrifluoroethylene (PCTFE),chlorotrifluoroethylene-perfluoroalkyl vinyl ether-tetrafluoroethylenecopolymer (CPT), tetrafluoroethylene-hexafluoropropene-vinylidenefluoride copolymer (THV), tetrafluoroethylene-hexafluoropropenecopolymer (FEP) or tetrafluoroethylene-perfluoroalkyl vinyl ethercopolymer (PFA). Also useful here are copolymers based on vinylidenefluoride that include up to 40% by weight of other monomers, for exampletrifluoroethylene, chlorotrifluoroethylene, ethylene, propene andhexafluoropropene.

The moulding compounds used in accordance with the invention may, aswell as polymer A or polymer B or polymer C, optionally comprise furtherpolymers and customary auxiliaries or additives. In a preferredembodiment, the moulding compound for the liner does not comprise anyfurther polymers aside from polymer A. In a further preferredembodiment, the moulding compounds both of the liner and of the tapesfor the first composite layer do not comprise any further polymers asidefrom polymer A or polymer B.

The film applied in step f) is a single-layer film in a firstembodiment, and a multilayer film in a second embodiment.

In the first embodiment, the thermoplastic component of the filmconsists of a moulding compound comprising at least 30% by weight,preferably at least 35% by weight and more preferably at least 40% byweight of polymer B, and at least 30% by weight, preferably at least 35%by weight and more preferably at least 40% by weight of polymer C, basedin each case on the overall moulding compound. Since polymers B and Care different, they are generally incompatible with one another. In thiscase, either the moulding compound has to comprise a compatibilizer, orthe two polymers B and C are at least partly joined to one another viachemical reactions.

One example of a moulding compound with compatibilizer is a mouldingcompound comprising a polyamide such as PA11 or PA12 to an extent of atleast 30% by weight, a fluoropolymer such as PVDF to an extent of atleast 30% by weight, and an effective amount of an acrylate copolymer.Suitable acrylate copolymers are disclosed, for example, in EP 0 673 762A2. It is possible, for example, for 0.1% to 10% by weight of theacrylate copolymer to be present in the moulding compound; in theproduction of the moulding compound, it is appropriate to premix thefluoropolymer and the acrylate copolymer in the melt.

One example of a moulding compound with chemical linkage is a mouldingcompound comprising a polyamide such as PA11 or PA12 to an extent of atleast 30% by weight and a semiaromatic polyamide or polyphthalamide(PPA) such as PA6T/6, PA6T/66, PA6T/61, PA6T/10T or PA6T/12 to an extentof at least 30% by weight. In the case of mixing in the melt, because ofthe high temperatures, transamidation reactions occur here, giving riseto block copolymers having PA11 or PA12 blocks and PPA blocks. These actas compatibilizers between the two components.

In the second embodiment, the multilayer film in the simplest caseconsists of two layers. It preferably consists of three layers. It mayalternatively consist of four, five or even more layers. There is onlyan upper limit to the number of layers in that it is impracticable toextrude layers of unlimited thinness. For reasons of practicability, theupper limit is therefore 9 layers and preferably 7 layers.

Examples of two-layer films are:

-   -   Layer oriented toward the first composite layer and composed of        a moulding compound comprising 50% to 80% by weight of polymer B        and 20% to 50% by weight of polymer C, and layer oriented toward        the second composite layer and composed of a moulding        composition comprising 50% to 80% by weight of polymer C and 20%        to 50% by weight of polymer B. The two moulding compounds        appropriately also comprise 0.1% to 10% by weight of a        compatibilizer. The percentages here, as in the examples which        follow, are based on the overall moulding compound for the        respective layer.    -   In the case of a first composite layer having an outer PVDF        surface, the layer of the film oriented toward the first        composite layer consists of a moulding compound comprising at        least 30% by weight of PVDF and 2.5% to 50% by weight of the        acrylate copolymer disclosed in EP 0 673 762 A2; the layer        oriented toward the second composite layer consists of the same        polyamide as the matrix of the second composite layer, for        example PA11 or PA12, to an extent of at least 50% by weight.    -   In the case of a first composite layer having an outer PPA        surface, the layer of the film oriented toward the first        composite layer consists of a moulding compound comprising at        least 40% by weight of the same PPA; the layer oriented toward        the second composite layer consists of the same polyamide as the        matrix of the second composite layer, for example PA11 or PA12,        to an extent of at least 50% by weight. Both moulding compounds        may additionally comprise 0.1% to 25% by weight of a        polyolefinic impact modifier containing acid anhydride groups.    -   In the case of a first composite layer having an outer PPS        surface, the layer of the film oriented toward the first        composite layer consists of a moulding compound comprising at        least 50% by weight of PPS and 3% to 30% by weight of a        polyolefinic impact modifier containing acid anhydride groups        that may also contain acrylate units (trade name, for example,        LOTADER®); the layer oriented toward the second composite layer        consists of the same polyamide as the matrix of the second        composite layer, for example PA11 or PA12, to an extent of at        least 50% by weight.    -   In the case of a first composite layer having an outer PA11 or        PA12 surface, the layer of the film oriented toward the first        composite layer consists of a moulding compound comprising the        same polyamide to an extent of at least 40% by weight and 30% to        60% by weight of a polypropylene or polyethylene containing acid        anhydride groups; the layer oriented toward the second composite        layer consists of the same polypropylene or polyethylene as the        matrix of the second composite layer to an extent of at least        50% by weight.    -   In the case of a first composite layer having an outer PEEK        surface, the layer of the film oriented toward the first        composite layer consists of a moulding compound comprising PEEK        to an extent of at least 30% by weight and a polyimide or        polyether imide to an extent of 20% to 70% by weight; the layer        oriented toward the second composite layer consists of the same        PPA as the matrix of the second composite layer to an extent of        at least 50% by weight, where the PPA for this layer preferably        has an excess of amino end groups to improve adhesion. The PPA        for the second composite layer may differ therefrom in terms of        the end group content.

Examples of three-layer films are:

-   -   Layer oriented toward the first composite layer and composed of        a moulding compound comprising at least 40% by weight of        polymer B. This is followed by an adhesion promoter layer        composed of a moulding compound comprising at least 30% by        weight of polymer B, at least 30% by weight of polymer C, and        optionally 0.1% to 20% by weight of compatibilizer. The layer        oriented toward the second composite layer comprises polymer C        to an extent of at least 40% by weight.    -   In the case of a first composite layer having an outer PVDF        surface, the layer of the film oriented toward the first        composite layer consists of a moulding compound comprising at        least 30% by weight and preferably at least 50% by weight of        PVDF. This is followed by an adhesion promoter layer composed of        an acrylate polymer according to EP 0 673 762 A2 or of a        polyamide/acrylate copolymer mixture according to EP 0 618 390        A1. The layer oriented toward the second composite layer        consists of the same polyamide as the matrix of the second        composite layer to an extent of at least 50% by weight; just        like the polyamide for the adhesion promoter layer; examples of        these are PA11 or PA12.    -   In the case of a first composite layer having an outer PPA        surface, the layer of the film oriented toward the first        composite layer consists of a moulding compound comprising at        least 40% by weight of the same PPA. This is followed by an        adhesion promoter layer composed of a moulding compound        comprising at least 30% by weight of this PPA and at least 30%        by weight of the polyamide to be bonded thereto. The layer        oriented toward the second composite layer consists of the same        polyamide as the matrix of the second composite layer, for        example PA11 or PA12, to an extent of at least 50% by weight.    -   In the case of a first composite layer having an outer PPS        surface, the layer of the film oriented toward the first        composite layer consists of a moulding compound comprising PPS        to an extent of at least 50% by weight. This is followed by an        adhesion promoter layer composed of a moulding compound        comprising at least 50% by weight of PPS and 3% to 30% by weight        of a polyolefinic impact modifier which contains acid anhydride        groups and may also contain acrylate units (trade name, for        example, LOTADER®). The layer oriented toward the second        composite layer consists of the same polyamide as the matrix of        the second composite layer to an extent of at least 50% by        weight, for example PA11 or PA12.    -   In the case of a first composite layer having an outer PA11 or        PA12 surface, the layer of the film oriented toward the first        composite layer consists of a moulding compound comprising the        same polyamide to an extent of at least 40% by weight. This is        followed by an adhesion promoter layer composed of an acid        anhydride-functionalized polyethylene (if the matrix of the        second composite layer is based on polyethylene) or an acid        anhydride-functionalized polypropylene (if the matrix of the        second composite layer is based on polypropylene). The layer        oriented toward the second composite layer consists of the same        polyethylene or polypropylene as the matrix of the second        composite layer to an extent of at least 50% by weight.    -   In the case of a first composite layer having an outer PEEK        surface, the layer of the film oriented toward the first        composite layer consists of a moulding compound comprising PEEK        to an extent of at least 40% by weight. This is followed by an        adhesion promoter layer composed of a moulding compound        comprising at least 50% by weight of a polyimide or polyether        imide. The layer oriented toward the second composite layer        consists of the same PPA as the matrix of the second composite        layer to an extent of at least 50% by weight, where the PPA for        this layer preferably contains an excess of amino end groups to        improve adhesion. The PPA of the matrix of the second composite        layer may differ therefrom in terms of the end group content.

The percentages by weight in these examples are merely illustrative;they can be varied according to the general figures given in the claimsand the description.

In the second embodiment, the liner and the first tape lamina of thefirst composite layer in step d) are likewise bonded by an appropriateintermediate film. The same details are applicable here as above for thefilm applied in step f); it is merely necessary to replace the term“first composite layer” with “liner”, “polymer B” with “polymer A”,“polymer C” with “polymer B”, and “second composite layer” with “firstcomposite layer”.

Single-layer films, in both embodiments, are produced in a known mannerby extrusion, and multilayer films in a likewise known manner bycoextrusion, extrusion coating or lamination.

The film to be applied is generally in the form of a tape. The film tapeis wound around the first composite layer or the liner in the form of aspiral, the angle being dependent on the tape width and the pipediameter. All that matters is to cover the outer surface of the firstcomposite layer or of the liner substantially seamlessly and preferablyvirtually completely seamlessly; the winding angle is unimportant inprinciple, provided that crease-free winding of this film lamina ispossible. Advantageously, the film is wound such that there is neitheroverlapping nor gaps. However, slight overlaps or gaps may possibly betolerated. The winding is effected under a contact pressure which isgenerated by the winding tension or by a pressing apparatus. In order toincrease the tensile strength of the film and hence prevent tearing ofthe softened film in the course of winding, one or more film layer(s)may contain unidirectional reinforcing fibres. In order not to worsenthe adhesion to the adjoining layers, however, it is advisable here notto choose too high a fibre content. In general, fibre contents in therange from 3% to 20% by volume are sufficient. A specific embodiment ofthis is a film composed of three or more layers where the middle layer(in the case of a three-layer film) or at least one of the middle layers(in the case of a film composed of more than three layers) comprisesunidirectional reinforcing fibres. In this case, the fibre content may,for example, be in the range from 3% to 40% by volume. Theunidirectional reinforcing fibres are generally oriented in axialdirection of the film tape. Multilayer films of this kind that comprisea fibre-reinforced layer can be produced, for example, by laminating theindividual layers, by extruding unreinforced layers onto a reinforcedlayer, or by extruding moulding compounds onto a spread fibre lamina.

In one possible embodiment, the film provided is bonded directly to thetape of the first tape lamina of the subsequent composite layer over anarea; in this case, the tape and the side of the film that is rich inthe corresponding polymer are welded to one another. In this embodiment,step d2) or step g) is undertaken. One advantage of this embodiment isthat the winding tension required cannot lead to breakage of the film,since it is reinforced by the tape. A composite of this kind can beproduced, for example, by laminating tape and film.

What is important is that both contact faces are melted in the weldingof first composite layer and film or of liner and film. In oneembodiment, the two contact faces are melted at the surface, for exampleby means of infrared radiation, hot air, hot gas, laser radiation,microwave radiation, or directly by contact heating. The contact facesthat have been melted at the surface are then pressed against oneanother, for example with the aid of the winding tension or by means ofa contact body, for instance a roller or a jaw. The contact pressureshould then be maintained until the molten regions have solidified. In afurther embodiment, the film is wound up and then melted from theoutside, either indirectly or else directly by means of a heatablecontact body. The heating output has to be calibrated such that theouter surface of the first composite layer or of the liner also startsto melt here. Thereafter, the contact pressure is maintained until theregions melted at the surface have solidified. This process can beconducted with the aid of a winding station and a downstreamconsolidation station, as described, for example, in WO 2012/118379.

The thickness of the film has to be sufficient to be able to absorb thewinding forces. On the other hand, the film has to be sufficientlyflexible. The film generally has a thickness in the range from 0.1 to 3mm, preferably in the range from 0.3 to 2 mm and more preferably in therange from 0.5 to 1.2 mm.

In step d2) or g), the tape is applied to the structure thus obtained,or to the surface of the film which is rich in polymer B [step d2)] orpolymer C [step g)], with application of a contact pressure. As in thecase of the film, the necessary contact pressure can be achieved throughthe winding tension or by means of a contact body. Here too, in oneembodiment, the two contact faces are melted at the surface, for exampleby means of infrared radiation, hot air, hot gas, laser radiation,microwave radiation, or directly by contact heating. The partly moltencontact surfaces are then pressed against one another. The contactpressure should then be maintained until the molten regions havesolidified. In a further embodiment, the tape is wound up and thenmelted from the outside, either indirectly or else directly by means ofa heatable contact body. The heating output has to be calibrated suchthat the outer surface of the previously applied film also starts tomelt here. Thereafter, the contact pressure is maintained until theregions melted at the surface have solidified. The winding of the tapeand the winding-up of any further tape laminas in steps e) and h) isprior art; no exact description of the procedure is therefore necessary.For details, reference is made to the prior art cited in theintroductory part of the description.

If required in terms of application, subsequently to step h), one ormore further composite layers having a matrix composed of a mouldingcompound based on another polymer can be applied if cohesive bonding tothe previous composite layer can be assured. For example, adhesion canbe generated in the same way as described above by means of a single- ormultilayer film of appropriate construction. In the case of thesefurther composite layers too, the proportion by volume of thereinforcing fibres in the tape is generally 10% to 85%, preferably 15%to 80%, more preferably 20% to 75% and especially preferably 25% to 70%,where the fibres are preferably in the form of a unidirectional fibrelamina.

In order to protect the outer composite layer, it is optionallypossible, finally, to apply a layer that adjoins the composite layer asouter cover lamina, composed of a reinforced or unreinforced polymericmaterial. This is either a thermoplastic moulding compound or athermoplastic or crosslinkable or crosslinked elastomer. The coverlamina preferably adheres firmly to the outer tape lamina. For thispurpose, it is advantageous to choose the material for the cover laminasuch that it comprises at least 30% by weight of the same polymer as inthe matrix for the outer composite layer or of a polymer compatibletherewith. In this case, the cover lamina may be applied, for example,by means of a crosshead extrusion die and hence be cohesively bonded tothe outer composite layer. If the cover lamina, however, is based on apolymer which is incompatible with the material for the outer compositelayer, it is possible, in the same way as described above, to generateadhesion by means of a single- or multilayer film of correspondingmakeup. Adhesion can also be generated by crosslinking of acrosslinkable elastomer.

The invention also provides a thermoplastic composite pipe which can beproduced using the process according to the invention. It comprises,from the inside outward, the following components:

-   a) a tubular liner having a wall comprising a thermoplastic polymer    A in the region of the outer surface;-   b) only if polymer A and polymer B are different, an intermediate    lamina which is directly and cohesively bonded to the liner and in    which the region of the contact area bonded to the liner consists of    a moulding compound comprising polymer A to an extent of at least    30% by weight, preferably to an extent of at least 40% by weight,    more preferably to an extent of at least 50% by weight, especially    preferably to an extent of at least 60% by weight and most    preferably to an extent of at least 70% by weight, and in which the    region of the opposite contact area bonded to the subsequent first    composite layer consists of a moulding compound comprising a    thermoplastic polymer B to an extent of at least 30% by weight,    preferably to an extent of at least 40% by weight, more preferably    to an extent of at least 50% by weight, especially preferably to an    extent of at least 60% by weight and most preferably to an extent of    at least 70% by weight;-   c) a first composite layer which is directly and cohesively bonded    to the outer liner surface or to the intermediate lamina and    comprises reinforcing fibres in a matrix comprising polymer B,-   d) an intermediate lamina which is directly and cohesively bonded to    the first composite layer and in which the region of the contact    area bonded to the first composite layer consists of a moulding    compound comprising polymer B to an extent of at least 30% by    weight, preferably to an extent of at least 40% by weight, more    preferably to an extent of at least 50% by weight, especially    preferably to an extent of at least 60% by weight and most    preferably to an extent of at least 70% by weight, and where the    region of the opposite contact area bonded to the second composite    layer consists of a moulding compound comprising a polymer C to an    extent of at least 30% by weight, preferably to an extent of at    least 40% by weight, more preferably to an extent of at least 50% by    weight, especially preferably to an extent of at least 60% by weight    and most preferably to an extent of at least 70% by weight;-   e) a second composite layer which is directly and cohesively bonded    to this intermediate lamina and comprises reinforcing fibres in a    matrix comprising polymer C,-   f) optionally an outer cover lamina composed of a polymeric    material,    where polymer A and polymer B are the same or different and polymer    B and polymer C are different.

Preferably, the thermoplastic composite pipe consists of components a)and c) to e) or a) and c) to f) (first embodiment) or of components a)to e) or a) to f) (second embodiment).

The individual configurations of this thermoplastic composite pipe willbe apparent from the above details relating to the production process.

In the process according to the invention, composite formation betweenidentical polymers in the critical process step achieves better qualityof adhesion. In addition, it is possible to use single-layer linerpipes. Existing large pipe extrusion plants can therefore continue to beutilized without modification. At the same time, it is possible tochoose less expensive polymers or polymers that are more favourable forapplication purposes than the polymer of the liner for the matrix of thecomposite lamina or of the second composite layer.

The pipe according to the invention is especially suitable for offshoreapplications in oil or gas production, for instance for transport of theproducts to platforms, for connection to steel pipes, as a transportpipe and especially, for example, as an umbilical, as a riser, as ajumper line, as a flowline, as an intervention line, as a downline, asan injection line or as a pressure line. The invention likewise providesfor the use for transport of possibly pressurized hydrocarbons ormixtures thereof, such as crude oil, crude gas, triphase (i.e.oil/gas/water mixture), processed oil (already partly processed at theseabed), processed gas, gasoline or diesel, of injection media such aswater (for instance to maintain the pressure in the cavern), oilfieldchemicals, methanol or CO₂, and for conduction of hydraulic oils (forexample for actuators at the seabed). Furthermore, the pipe according tothe invention is also suitable as a pressure-conducting line in theonshore sector or in other industrial applications, especially in thosewhere relatively high forces have to be transmitted in the axial pipedirection with force-fitting bonding between the pipe and connectionelement.

The invention claimed is:
 1. A process for producing a thermoplasticcomposite pipe, the process comprising: (i) applying a first compositelayer comprising a first tape to a tubular liner via welding, and (ii)applying a second composite layer, which is produced by applying asecond tape to an outer surface of a first film and melting the outersurface of the first film and a contact surface of the second tapeeither beforehand, simultaneously or thereafter, to the first compositelayer and melting an outer surface of the first composite layer and acontact surface of the first film either beforehand, simultaneously orthereafter, wherein the tubular liner has a wall comprising athermoplastic polymer A in a region of an outer surface thereof, thefirst tape comprises reinforcing fibres in a matrix comprising athermoplastic polymer B, the second tape comprises reinforcing fibres ina matrix comprising a thermoplastic polymer C, the polymer A and thepolymer B are the same or different, the polymer B and the polymer C aredifferent, and the surface of the first film which is brought intocontact with the first composite layer consists of a moulding compoundcomprising at least 30% by weight of the polymer B, and the oppositesurface of the first film consists of a moulding compound comprising atleast 30% by weight of the polymer C.
 2. The process according to claim1, wherein the second composite layer is produced by bonding the firstfilm and the second tape over an area such that the second tape and aside of the first film that contains more of the polymer C are welded toone another.
 3. The process according to claim 1, wherein the polymer Aand the polymer B are different; said applying (i) is performed byapplying the first composite layer, which is produced by applying thefirst tape to an outer surface of a second film and melting the outersurface of the second film and a contact surface of the first tapeeither beforehand, simultaneously or thereafter, to the tubular linerand melting an outer surface of the tubular liner and a contact surfaceof the second film either beforehand, simultaneously or thereafter; andthe surface of the second film which is brought into contact with thetubular liner consists of a moulding compound comprising at least 30% byweight of the polymer A, and the opposite surface of the second filmconsists of a moulding compound comprising at least 30% by weight of thepolymer B.
 4. The process according to claim 3, wherein the first filmand the second film consist of two, three or more layers cohesivelybonded to one another.
 5. The process according to claim 3, wherein atleast one of the first film and the second film comprises unidirectionalreinforcing fibres.
 6. The process according to claim 1, furthercomprising: (iii) finally applying an outer cover lamina comprising apolymeric material.
 7. The process according to claim 1, wherein thepolymer A is selected from the group consisting of polyolefin,polyamide, polyphthalamide, polyethylene naphthalate, polybutylenenaphthalate, fluoropolymer, polyphenylene sulphide, polyether sulphone,polyphenyl sulphone, and polyarylene ether ketone.
 8. The processaccording to claim 1, wherein the polymer B is selected from the groupconsisting of polyolefin, polyamide, polyphthalamide, polyethylenenaphthalate, polybutylene naphthalate, fluoropolymer, polyphenylenesulphide, polyether sulphone, polyphenyl sulphone, and polyarylene etherketone.
 9. The process according to claim 1, wherein the polymer C isselected from the group consisting of polyolefin, polyamide,polyphthalamide, polyethylene naphthalate, polybutylene naphthalate,fluoropolymer, polyphenylene sulphide, polyether sulphone, polyphenylsulphone, and polyarylene ether ketone.
 10. The process according toclaim 1, wherein the reinforcing fibres in at least one of the firsttape and the second tape are unidirectionally arranged.
 11. The processaccording to claim 1, wherein an amount of the reinforcing fibres in thefirst tape or the second tape is 10% to 85% by volume.
 12. The processaccording to claim 1, wherein the reinforcing fibres in the first tapeor the second tape are selected from the group consisting of glassfibres, carbon fibres, aramid fibres, boron fibres, ceramic fibres,basalt fibres, silicon carbide fibres, polyamide fibres, polyesterfibres, fibres of liquid-crystalline polyester, polyacrylonitrilefibres, polyimide fibres, polyetherimide fibres, polyphenylene sulphidefibres, polyether ketone fibres, and polyether ether ketone fibres. 13.The process according to claim 1, further comprising (iv) after saidapplying (i) and before said applying (ii), cohesively bonding furthertape laminas that are of the same kind as the first tape.
 14. Theprocess according to claim 1, further comprising (v) after said applying(ii), cohesively bonding further tape laminas that are of the same asthe second tape.
 15. The process according to claim 1, wherein the firstfilm is a single-layer film.
 16. The process according to claim 1,wherein the first film is a multi-layer film.